Hibernate JPA @LazyCollection Example

@LazyCollection

The @LazyCollection annotation is used to specify the lazy fetching behavior of a given collection. The possible values are given by the LazyCollectionOption enumeration:

TRUE
Load it when the state is requested.

FALSE
Eagerly load it.

EXTRA
Prefer extra queries over full collection loading.

The TRUE and FALSE values are deprecated since you should be using the JPA FetchType attribute of the @ElementCollection, @OneToMany, or @ManyToMany collection.

The EXTRA value has no equivalent in the JPA specification, and it’s used to avoid loading the entire collection even when the collection is accessed for the first time. Each element is fetched individually using a secondary query.

LazyCollection mapping example

@Entity(name = "Department")
public static class Department {

@Id
private Long id;

@OneToMany(mappedBy = "department", cascade = CascadeType.ALL)
@OrderColumn(name = "order_id")
@LazyCollection( LazyCollectionOption.EXTRA )
private List<Employee> employees = new ArrayList<>();

//Getters and setters omitted for brevity

}

@Entity(name = "Employee")
public static class Employee {

@Id
private Long id;

@NaturalId
private String username;

@ManyToOne(fetch = FetchType.LAZY)
private Department department;

//Getters and setters omitted for brevity

}